Static suppressor



June 13, 1933. C. S. WOLFE STATIC SUPPRESSOR Filed May 10, 1930 dill} FIG. I.

FIG. 2.

gwuento'c CHARLES s. WOLFE yaw fli/ f ducnmq Patented June 13, 1933 UNITED STATES PATENT OFFICE CHARLES s. WOLFE, 0F NORRISTOWN, PENNSYLVANIALASLSIGNOR "1'0 BURDP. EVANS, OF TRAPPE. PENNSYL ANIA STATIC surrnnsson Application filed May 10,

An object of my invention is to devise a system which may be incorporated in the audio frequency circuit of a radio receiving apparatus for effectively reducing the effects of interfering currents due to static and other impulses.

A further object of my invention is to devise a static suppressor arrangement which may be manufactured and sold as an independent unit and inserted between existing radio sets and their loud speakers.

In accomplishing the objects of my invention I employ a special transformer connected in the audio frequency output circuit of a radio receiving apparatus, the transformer having two secondary windings, one of which is connected directly to the reproducing apparatus or loud speaker, and the other connected to the reproducer through a triggerlike element in opposing relation to the first secondary winding.

During normal operation, the trigger-like element possesses high internal resistance, and substantially no current is supplied to the loud speaker by the second secondary winding. Upon the receipt of a static or other impulse superimposed upon the normal signal strength, the resistance of the trigger-like element automatically reduices and permits the flow of current from the second secondary to oppose the current supplied by the first secondary winding.

My invention is illustrated in the accompanying drawing in which:

Figure 1 is a circuit diagram illustrating one form of the invention, and i Figure 2 is a circuit diagram illustrating a second form of the invention.

Referring to Figure 1, 1 indicates a radio receiving apparatus which may comprise known types of radio receivers including the usual amplifying and detecting apparatus. To the low frequency output circuit of receiver 1 is connected a transformer 2 having a primary winding 3 and two secondar windings 4 and 5. Transformer 2 is pre 1930. Serial No. 451,415.

erably provided with an iron core and So designed that the magnetic leakage is reduced to a minimum. Secondary windings 4 and 5 are also preferably wound in bifilar fashion in order that they shall be substantially identical in every respect. Winding 4 is connected directly to a loud speaker 6 or other reproducing apparatus by wires 4a and 4b. The beginning of secondary windin 5 is connected to the end of secondary wmding 4 by connecti on 5a, and the end of secondary windingg5 is connected to beginning of winding 4 through a trigger-like element represented within the dotted square 7. It will thus be seen that windings 4 and 5 are connected in '65 opposing relation to the loud speaker 6 with the trigger-like element 7 interposed 'in the connection between the loud speakerand secondary winding 5.

The trigger-like element 7 is a device which possesses high internal resistance for applied voltages up to certain value, and above this value the internal resistance automatically reduces and permits the flow of current.

Various devices possessing this cliaracteristio may be incorporated in my system; it being essential, however, that the device'have this characteristic in both directions. I have obtained good results with a variable" carbon contact resistance, and also with a variable 8'0 water rheostat resistance. In Figure 1 I have diagrammatically illustrated a combination of devices which I have also found to give "good results. i In the combination shown in the dotted square, 7a indicates a variable 35 carbon contact resistance connected in series circuit relation with two neon lamps 7b. The neon lamps are normally energized from a source of current 70, which may be either a source of direct current or a source'of' alter-" the secondary winding 5. As indicated'95 above, satisfactory operation'ma'y' be obtained by employing carbon contact resistance7a alone, or by employing theneon lamp arrangement alone. It is understood that only one neon lamp may be used instead of two as shown, or two or more lamps may be connected in parallel.

Operation of Figure 1 is as follows: The current supplied to the neon lamps 7b is adjusted until the lamps are operating just at the critical point at which the internal resistance is very high, but upon the application of additional potential across the terminals, the internal resistance drops and permits the flow of current through the lamp. Under normal operation therefore, the signal strength is not sullicient to lower the internal resistance of the lamps 7b and to permit substantial current to be supplied by this winding; the loud speaker being operated substantially entirely from Winding 4. Upon :the receipt of a disturbing impulse, however, the internal resistance of lamp 7?) is reduced, and winding-5 is thereby effectively connected in parallel in opposing relation with winding and the impulse in one winding opposes the impulse in the other. After the passage of the impulse, the normal resistance conditions are restored, and the loudspeaker continuesito operate on the winding 4. Since the trigger-device 7 has the same characteristic in both directions, the arrangement will operate effectively .to prevent disturbances in the loud speaker by impulses of either polarity.

In addition to the devices mentioned above, certain electrolytic cells are known to possess the bi-l-ateral trigger-like conduction characteristic necessary for the operation of my invention, and such devices may be employed if desired.

In Figure 2 I have illustrated a modified form of my invention in which the circuit of secondary winding 5 normally remains open,

erably filled with neon gas, and will produce a glow when energizedto a definite degree. An amplifier 11 is inserted between photoelectric cell 9 and the relay 8 to amplify the feeble current generated in the cell circuit.

Operation of Figure 2 is as follows: Under operation with normal signal strength, the .eflect of lamp 10 upon cell 9 is not sufiicient to operate relay 8. Upon the receipt of a disturbing impulse superimposed upon the normal signal, lamp 10 will glow brighter and thereby increase the current generated in the cell circuit and cause the operation of relay 8. Secondary winding 5 will therefore, be connected in parallel with winding 4 in opposing relation to effectively prevent a disturbance by the impulse upon the loud speaker. After the impulse has passed, the circuits will be restored to their normal condition and winding '5 disconnected from the loud speaker.

It will be understood by one skilled in the art that the two circuits from the secondary windingto the loud speaker must be balanced, and for this purpose, adjustable resistances or impedances may be inserted in one or both circuits for the purpose of obtaining a proper balance. In order to obtain effective neutralization of the impulse, the two circuits must transmit impulse currents substantially 180 degrees out of phase and of substantially the same amplitude. I find that it is easier to obtain a balance by employin-g non-inductive resistance elements in the circuits.

lVhile I have described my invention as applied to a radio receiver for suppressing disturbanoes due to static and other impulses, it is apparent that the device may be used at the receiving end of a telephone or telegraph line for suppressing disturbances due to current or voltage impulses of whatever origin. It is also to be understood that while I have illustrated and explained my invention in c0- operation with a loud speaker, the invention is not limited in its application to any particular form of translating device.

It is not essential that the trigger-like device be perfect in its operation, that is, that it possess infinite resistance up to a certain voltage and then very low resistance above that voltage, but it will be understood that a certain current may flow through the device under normal signal strength operation but not of sufiicient value to substantially reduce the signal strength at the loud speaker.

What I claim is:

1. An impulse suppressor comprising input and output terminals, a transformer hav ing a primary winding connected to said input terminals, a secondary winding connected to said output terminals, a second secondary winding connected to said output terminals in opposing relation to the first and having in series therewith a. bi-lateral conductor element of fixed physical dimensions, said element having normally high resistance and being characterized by a substantial reduc tion in resistance upon the application ofvoltage above a certain value, and electric means for varying the break down voltage of said element.

2. In a signaling system. the combination of a circuit for collecting signal current sub-' rents are not substantially transmitted by said T circuit, but abnormal impulses render said device effective to transmit current through said circuit.

3. In a signaling system, the combination of a; circuit for collecting signal current subject to disturbing impulses, a detector connected to said collector circuit, a transformer connected to said detector for receiving detected low frequency signals, said transformer having two secondary windings, a signal translating device connected to one of said secondary windings, said second sec ondary winding being connected to said translating device in opposed relation to said first secondary winding, a normally non-conductive gaseous discharge device connected in series with the circuit of one of said secondary windings, and means for normally biasing said discharge device to a critical condition whereby the application of a potential above critical. value renders the discharge device substantially conductive.

4. In a signaling system, the combination of a circuit for collecting signal current subject to disturbing impulses, a detector connected to said collector circuit, a transformer connected to said detector for receiving detected low frequency signals, said transformer having two secondary windings, a signal translating device connected to one of said secondary windings, said second secondary winding being connected to said translating device in opposed relation to said first secondary winding, a normally non-con ductive gaseous discharge device connected in series with the circuit of one of said second ary windings, said discharge device comprising an evacuated envelope containing a pair of spaced electrodes in the gaseous atmosphere, and an adjustable source of current connected across said electrodes for normally biasin said discharge device to a critical condition whereby the application of a potential above a critical value renders the dis- 4 charge device substantially conductive.

In witness whereof I affix my signature.

CHARLES S. WOLFE. 

